Hydraulic apparatus



Oct, 29, 1968 J, D. NORTH ETL 3,407,745

HYDRAULIC APPARATUS huvEN-rozi S'DHN ID. NoRf/ DeN/Hs T. MJLLARD Y M4."MT' M" AT-rozNn-ws United States Patent O `3,407,745 HYDRAULIC APPARATUSJohn D. North, Eversley, Bridgnorth, and Dennis J. Millard, Finchield,Wolverhampton, England, assignors to Boulton Paul Aircraft Limited,Wolverhampton, England Filed July 18, 1966, Ser. No. 570,385 Claimspriority, application Great Britain, July 27, 1965,

32,049/65; Sept. 14, 1965, 39,169/65 7 Claims. (Cl. 103-162) ABSTRACT FTHE DISCLOSURE A hydraulic machine is dis-c-losed which includes arotatable cylinder block having cylinders therein and a fixed swashplate adjacent each end of the block. Ateach end of the block pistonsproject from cylinders opening thereinto, and the pistons engage theadjacent swasliplates in such a way that rotation of the block inducestheir reciprocation in the cylinders. In addition, there is a casingwhich rigidly secures the swash plates together in a xed spacedrelationshipV and encloses the cylinder block. The cylinder block isrigidly supported on bearings by virtue of there being (l) a fixedbearing support extending into a recess in one end of the block from theadjacent swash plate and a bearing engaged between the recess and thesupport, and (2) a shaft extending from the other end of the blockthrough a hole in the adjacent swash plate and a bearing engaged betweenthe shaft and the hole. Valve means are movably supported on the bearingsupport for connecting the cylinders in the block alternately to supplyand return passages for liquid extending through the bearing support.yThe cylinders are alternately connected in synchronism with rotation ofthe block and reciprocation of the pistons in the cylinders.

This invention relates to hydraulic pumps and hydraulic motors of theswash plate type. Hydraulic pumps or motors ,are known which comprise arotatable cylinder block having cylinders therein parallel to the blockaxis, a first swash plate adjacent to one end of the block .andengageable by pistons projecting from the cylinders which openV intothat end of the block and a second swash plate adjacent the other end ofthe block and engageable by pistons projecting from the cylinders whichopen into said other end of the block whereby rotation of the blockinduces lreciprocation of the pistons in the cylinders. It has also beenproposed that such a swash plate pump or motor should include a valvelocated in a recess within the block. The main purpose for theconstruction of a pump or motor, as above described, is to provide apump or motor of compact dimensions for a required liquid volumetricdisplacement per revolution. However in these earlier proposals therotatable cylinder block was provided with a shaft or axle extendingfrom both ends thereof The object of the present invention is to providea pump or motor, as described above, in which the shaft extends from oneend only of the cylinder block, thereby to reduce the total overalllength of the pump or motor in a direction parallel to the rotationaxis.

In accordance with the present invention, a hydraulic pump or ahydraulic motor includes a rotatable cylinder block having cylinderstherein, a first swash plate adjacent to one end of the block andengageable by pistons projecting from the cylinders which open into thatend and a second swash plate adjacent to the other end of the block andengageable by pistons projecting from the cylinders which open into saidother end of the block, whereby rotation of the block inducesreciprocation of the pistons in the cylinders, bearing means for theblock disposed within a recess in anv end of the block and valve meansmovably 3,407,745 Patented Oct. 29, 1968 ice supported on the bearingmeans for connecting the cylinders in the block, alternately to a supplypassage for liquid and a return passage for liquid in synchronism withthe reciprocation of the pistons in the cylinders.

The bearing means may be a bearing support extending into the recess anda ball or roller bearing acting between a part of the support and a partof the Wall of the recess. The ball or roller bearing is preferablylocated to lie substantially or entirely on the cylinder block side of aplane which intersects the rotational axis perpendicularly at the pointof intersection of the rotational axis with the second swash platesurface.

The valve means may comprise a valve plate mounted on the bearingsupport in the recess for axial and tilting movement to engage a flatvalve surface formed on the block in the recess, the plate includingsupply and return points connected to supply and return passagesextending through the support and the valve surface including cylinderports extending one from each cylinder. Y

The cylinder ports may be formed in a cylinder port plate secured in therecess and having ports co-operating with passages extending to thecylinders.

The cylinder port plate is preferably made an interference fit withinthe recess so that the cylinder ports sealingly connect with thecylinder passages.

Preferably the cylinders each extend from end to end of the 4block andeach include a pair of pistons extending one from each end of the block.

A drive shaft may extend from the end of the block opposite to therecess for transmission of the driving torque to or from the block.Preferably the cylinder block is of forged metal land the recess isformed roughly during forging such that the displaced metal extends fromthe opposite end of the block to form the drive shaft.

The drive shaft may be located by a bearing spaced from the cylinderblock.

The bearing associated with the shaft may be adapted to resist endthrust such for example .as may be generated by the valve plate.

How the invention can be carried into effect will hereinafter beparticularly described with reference to the accompanying drawings, inwhich,

FIGURE l is a longitudinal cross-section through one embodiment of theinvention intended particularly for use as a motor,

FIGURE 2 is a plan view of a detail employed in FIG- URE 1 and,

FIGURE 3 is a cross-section through another embodiment of the inventionalso for use as a motor.

Reference is made initially to FIGURES l and 2 of the drawings. Acylindrical motor casing 1 includes at either end an inwardly-directedflange respectively 2 and 3 A swash plate 4 is engaged within the casing1 against the ilange 2 and a swash plate 5 is engaged within the casingagainst the flange 3. For purposes .of assembly, the casing 1 is splitin a diametrical plane, but details of the split do not appear in thedrawings. A central hole 6 extends through the swash plate 4 andencloses a taper roller bearing 7 within which a drive shaft 8 isrotatably mounted, the axis of the drive shaft being parallel to thelongitudinal axis of the casing 1. Within the casing 1 the drive shaft 8is connected tixedly to a rotary cylinder block 9 or may be integraltherewith.

The cylinder block 9 includes a plurality of cylinders 11 each parallelto the block rotation axis and bored through the block from end to end.Within each cylinder 11 a pair of pistons 12 and 13 are slidabllymounted, these pistons being urged apart by a compression spring 14within the cylinder. The outer ends of the pistons 12 and 13 are eachsocketed respectively at 15 and 16 to receive respectively the ball endsof slippers 17 and 18. The slippers 17 engages the inclined cam surface19 of -swash plate 4.7l`he slippers 1 8 engage the inclined cam surface21 of the swash plate 5. A xed bearing member 22 is integrally formedwithy the swash plate 5 and enters a vcentral recess 26 formed in thecylinder block 9 at the end opposite to the drive shaft 8. Preferablythecylinder block 9and 4the shaft 8 are made as a single forging, thedisplacement of metal during formation of the recess 26 causingextrusion of metal from the other end, of the, block toform the shaft,8. Securely xed within the base of the recess 26 isp avalve member 2,7within which are formed passages 28 leading one to the centre ofeachcylinder 11 andterminatingas ports. 29 in a flat block surface 31,extending perpendicular to the axis of block rotation. The passages 28each make a sealed connection to a passage 23 extending in the block 1from the centre of each cylinder 11. The valve member 27 is preferablyarranged to.be an interference fit within the recess 26 to ensuresealing engagement between the pas- VSages 2,8 and 23. A pluralityof-bolts 24 Ymay be provided extending through the valve member 27 intothe block to ensure that itvremains in position. Grooves S in thebase of.the valve member 27 prevent build u-p of pressure by leakage whichotherwise might move the member 27 axially.

The bearing member 22 includes a pair of passages 32 and 33 extendingfrom the outer to the inner ends thereof, these passages performingsupply and return functions for liquid fed to the motor. At the innerend of the member 22 the passages 32 and 33 each have a shortcylindrical sleeve respectively 34 and 35 lixedly secured therein toextend parallel to the rotation axis. On the end of the sleeves 34 and35 a valve plate 36 is mounted by means of recesses 37 and 38 in thevalve plate. The sleeves 34 and 35 includes seals which ensure theirengagement in the recesses 37 and 38 in a liquid tight manner. The face39 of the valve plate opposite to the sleeves 34 and 35 is formed as aat valve surface which engages the block surface 31. Within the valvesurface supply and return ports 41 and 42 are formed, these ports beingof conventional or kidney shape for engagement by cylinder ports 29. Ataper roller bearing 44 engages between the bearing member 22 and theoutermost part of the recess 26. It will be noted that the rollerbearing 44 is located on the support 22 on the cylinder block side of aplane A-B which intersects the rotation axis perpendicularly at thepoint where the plane swash plate surface 21 intersects the rotationaxis. By this means substantially the entire radial force generated bythe engagement of the slippers 18 on the swash plate surface 21 istransferred directly through the bearing 44 to the support '22.

The cross-section through the bearing member 22 is shown in a plane atright angles to the cross-section through the remainder of FIGURE 1 inorder to show more conveniently the sleeves 34 and 35 and the ports 41and 42. Normally these sleeves and these ports would not appear in thesection of FIGURE l.

Each of the slippers 17 and 18 includes a deep circumferential groove-45which is engaged by a slipper plate 46. A part of the slipper plate 46is shown in plan view in FIGURE 2. Generally the slipper plate 46 is inthe form of an annulus having recesses 47 opening from itscircumference. The recesses 47 fit around the bottoms of the grooves 45to ensure substantial engagement between the plate 46 and both sides ofeach groove 45 in each slipper. The function of the plate 46 is toassist in holding each slipper 18 in contact with its swash platesurface. It will be appreciated that in operation only some of thepistons will receive liquid under pressure which will urge themoutwardly so that their slippers engage the adjacent swash platesurface. The few slippers that are strongly held by their pistonsagainst the swash plate surface will act on the slipper plate 46 to holdit or tend to hold it parallel to the swash plate surface. The forcesexerted will react on all other CII slippers adjacent to that swashplate to hold them, or tend to hold them, against the swash platesurface. In the described embodiment the sockets 15 and 16 in the endsof the piston are arranged so as not to be capable of retaining .theslippers if a ,pulling force is exertedron the slipper by the plate 46to move it out of the recess. The springs 14 act on their associated`pistons always to urge them outwardly to tend yto ensure thatthesockets 15 and 16always engage'their respectiveslippers. However, thesprings are not a positive assurance that the piitons will always engagetheir respective slippers since if the unit described is to act as apump and suction has to be exer'fed on' liquid to'c'ause it to entef thecylinders, the occasion might arise when the ,springs 14 cannot exert asufficient force to provide the necessary suction and theseslippers'rnay then disengage from their pistons. Alternatively, if theunit acts as a pump and is driven at high speed, it can well occur thatthe springs 14 are not of sufcient strength to urge the piston out ofthe cylinders in the short period available for the outward strokeagainst the inertia of the pistons, Again the slippers would thendisconnect from their pistons. A guard ring 48 is fixed to the peripheryof each swash plate surface 19 and 21 to engage the slippers in theeventthat they then tend to centrifuge outwardly from the plate 46 ifdisengaged from their pistons. The guard ring 48 extends over aboutthree-quarters of the circumference of the swash plate surfaces atpositions where the slippers extend substantially from the cylinders. Atthe positions where the slippers are almost fully in the cylinders, asshown, on the bottom cylinders, of FIGURE 1, the guard ring isunnecessary.

At positions lbetween the recesses 47 parts of the circumference of theslipper plate 46 are reduced in thickness, as shown at 49. The purposeof these reductions in thickness is to avoid actual contact between theslipper plate and the cylinder block between adjacent cylinders at theinnermost positions of the pistons. The reduced portions 49 again serveto enable the swash plates tobe located very close to the cylinder blockthus reducing total overall length.

In operation of the motor,v liquid at pressure is supplied to one of thepassages 32 and 33 depending on the direction of rotation desired andreturn liquid at low pressure is taken from the other passage. Assumethat such high pressure liquid is supplied to the connection 32. Thepressure liquid passes through the sleeve'34 and in the recess 37 willact on the valve plate 36 to urge it into engagement with the blocksurface 31. Liquid from therecess 37 will then pass through the mainport 4'1 into the cylinder ports 29 which are in connection with it.Liquid at pressure will then be conveyed to all'cylinders whose pistonswill move outwardly with the desired rotation vof the cylinder block byvirtue of the slopes of the cam surface 19 and 21. The cylinders inconnection with the other port 42 will discharge liquid at low pressureinto the passage 33 since their pistons will move inwardly by virtue oftheir engagement with the cam surfaces. The cross-sectional area of therrecess 37 which engages on the sleeve 34 is so chosen in relation tothecross-sectional area of port 41 that the valve plate 36 is held with aslight excess of hydraulic force on the block surface 31. Since thecylinders are all of constant diameter and they each include two pistonsacting oppositely on the surfaces 19 and 21, no resultant axialhydraulic force reacts on the cylinder block from' the pistons. Howeverthe pressure of liquid acting in the port 41 produces a force which istransferred to thel block itself. This axial force is `resisted by thetaper roller bearing 7. The radial thrust exerted on the cylinder blockby virtue of the engagement of the pistons with the cam surfaces 19 and21 are re-acted through the taper roller bearings 7 and 44. The cylinderblock 9 is therefore located in the casing by the bearings 7 and 44 forrotation only, any other movements of the block being resisted by thebearings. The valve plate 39 is free to tilt and to move axially on thesleeves 34 and 35 to engage the block surface 31 quite independently ofany radial thrust exerted through the taper roller bearing 44 and anyslight deflections that might occur of the bearing support 22.

Reference is now made to FIGURE 3 of the accompanying drawings. Thisgure shows a motor which differs in detail only from the motor shown inFIGURES 1 and 2. Detailed description of FIGURE 3 is not proposed exceptto point out the essential differences in structure. Where possiblesimilar reference numerals in FIGURES 1 and 3 will refer to similarparts thereof. In FIGURE 3 the support member 22 is not integral withthe swash plate 5 but is made as a separate `item for fixing to theswash plate 5. For this purpose a central hole 51 is provided in theswash plate 5 to receive the support member 22. A flange 52 around thesupport member 22 is secured by bolts 53 to the swash plate S. In FIGURE3 the bearing 44 in the recess 26 is a parallel roller bearing ratherthan a taper roller bearing and it is located more closely to the planeA-B than is the bearing 44 in FIGURE 1. In FIGURE 3 no slipper rings areemployed to locate the slippers but alternatively the recesses and 16 inthe ends of the pistons 12 and 13 are provided With circlips 54 whichlocate the ball ends of the slippers in the recesses so that there is nodanger of the slippers parting from their associated pistons. On theoccasions when the springs 14 are not able to urge the pistons outsufliciently quickly during pump action of the illustrated unit, theslippers will part from the cam surfaces for short periods duringrotation.

In FIGURE 3 the cylinder port plate 27 rests on a shoulder in the bottomof the bore 26 which includes relief recesses 55 whose function is toprevent build-up of liquid pressure behind the port plate 27 which mightmove it axially. Central holes 56 in the port plate 27 and 57 in thevalve plate 36 will vent any such leakage liquid to the interior of thecasing from whence it is drained by a suitable drain connection.

In FIGURE 3, as in FIGURE 1, the cross-section through the bearingsupport 22 is shown in a plane at right-angles to the cross-section ofthe remainder of the drawing.

The operation of the FIGURE 3 embodiment of the invention issubstantially the same as that described for the FIGURE 1 embodiment.

In a further modiiied form of motor the cylinders 11 are of stepped formso that the ends of the cylinders adjacent to the bearing member 22 areof slightly smaller diameter than the ends of the cylinders adjacent thedrive shaft 8. The difference in diameter of the cylinders is socalculated that the total axial thrust exerted by the pistons and therecesses 37 and 38 under pressure is extremely small. In this way thetaper roller bearings 7 and 44 of FIGURE 1 or the bearing 7 of FIGURE 3can be relieved of substantially all axial load.

Whilst in the described embodiments the valve plate is secured againstrotation about the block axis, it is within the scope of the presentinvention for the valve plate to be adjustable through a small angleabout the block axis t0 vary the phasing between reciprocation of thepistons and the connection of the cylinders to the supply and returnports in order to vary the effective hydraulic displacement perrevolution of the pump or motor. For this purpose the support 22 may berotatably mounted in the swash plate 5.

In the described embodiment the cylinder block is supported by the twobearings 7 and 44 of which the bearing 7 is external of the block. In amodied form of the invention the block may be supported completely byinternal bearings between the Support 22 and the block. Rotary drivingtorque may then be transmitted to or from the block by means of gearteeth disposed around the periphery of the block.

Whilst the valve means in the illustrated embodiments 6 is of the facevalvetype hydraulically urged into engagement with the face 31 of theblock it is within the scope of the present invention that the valvemeans may take any other conventional form. For example, it could be asimple pintle valve engaging in a cylindrical valve surface in theblock.

In the described embodiment the cylinders 11 are shown to extendcompletely through the cylinder block. However it is possiblerto modifythis arrangement by providing for example :separate cylinders extendinginto the block from the two ends thereof. Such cylinders may -be eitherparallel to or inclined to the block rotation axis.

What is claimed is:

1. A hydraulic machine including a rotatable cylinder block havingcylinders therein, a first fixed swash plate adjacent to one axial endof the block, pistons projecting from cylinders which open into said oneend of the Iblock and engaging the rst swash plate, a second fixed swashplate adjacent to the other end of the block, pistons projecting fromcylinders which open into said other end of the block and engaging thesecond swash plate, whereby rotation of the block induces reciprocationof the pistons in the cylinders, a casing enclosing the cylinder blockand rigidly securing the swash plates together in fixed spacedlrelationship to one another, a bearing support xedly connected to thefirst swash plate and extending from the latter swash plate into arecess in the one end of the block, a bearing engaged between theperipheries of the recess and the support and acting as the sole meansfor supporting axial and radial forces imposed on the one axial end ofsaid cylinder block, a valve means supported on the bearing support foraxial movement in relation thereto, whereby the cylinders in the blockare alternately connected to a supply passage for liquid and a returnpassage for liquid extending through the bearing support in synchronismwith rotation of the block and reciprocation of the pistons in thecylinders, a shaft extending from the said other end of the blockthrough a hole in the second swash plate, and a bearing engaged betweenthe shaft and the hole.

2. A hydraulic machine as claimed in claim 1 wherein the bearing betweenthe recess and the support is arranged to lie substantially or entirelyon the cylinder block side of a plane which intersects the rotation axisperpendicularly at the point of intersection of the rotation axis withthe first swash plate surface.

3. A hydraulic machine, as claimed in claim 1, including a cylinder portplate ixedly connected to the block in the recess thereof, and havingone `surface forming the said block surface, the ports in the port platehaving connecting passages to the cylinders.

4. A hydraulic machine, as claimed in claim 3, wherein the port plate isan interference t within the recess.

5. A hydraulic machine as claimed in claim 1 wherein the valve meanscomprises a circular valve plate mounted on the vbearing support foraxial and til-ting movement in relation thereto so as to 4continuouslyengage a flat surface formed on the block, the bearing support being ofcylindrical shape andl the valve plate being `disposed wholly Within therecess and at least as large in diameter as the bearing support.

6. A hydraulic machine as claimed in claim 1 wherein the bearings eachcomprise a taper roller bearing disposed to accommodate vboth axial andradial thrust from the block.

7. A hydraulic machine including a rotatable cylinder block havingcylinders therein, a rst xed swash plate adjacent to one end of theblock, pistons projecting from cylinders which open into said one end ofthe block and engaging the first swash plate, a second fixed swash plateadjacent to the other end of the block, pistons projecting fromcylinders which open into said other end of the block and engaging thesecond swash plate whereby rotation of the block induces reciprocationof the pistons in the cylinders, a casing rigidly securing the swash 7plates together in a xed spaced relation and enclosing the cylinderblock, a fixed bearing support extending into a recess in the one end ofthe block from the first swash plate, a bearing engaged between therecess and the support, a valve means movably supported on the bearingsupport-for connecting the cylinders in the block alternately to `asupply passage for liquid and a return passage for, liquid extendingthrough the bearing support in synchronism with rotation of the blockand reciproca tion of the pistons in the cylinders, a shaft extendingfrom the said other end of the block through a hole in the second swashplate, ka bearing engaged between the shaft and the hole, a slipperplate recessed at a plurality of positions around its periphery to t ingrooves formed in the slippers engaging a swash plate whereby slippersloaded against the swash plate by their pistons will act through theslipper plate to hold the other slippers against the swash plate, and aguard ring secured to the swash plate and at least partly surroundingthe swash 8 Yplate surface to limit outward centrifuging of the slippersengaging the swash plate.

References Cited UNITED STATES PATENTS 1,822,064 9/1931 Sorensen 103-1622,273,468 2/1942 Ferris 103-161 A2,915,985 12/1959 Budzich 103-1623,166,016 l/l965 Thoma 103-162 3,200,762 8/1965 Thoma 103-162 3,207,0829/'1965 Budzieh et al. 103--162 FOREIGN PATENTS 1,302,652 7/1962 France.1,343,916 11/1963 France. 622,787 7/1961 Italy.

WILLIAM L. FREEH, Primary Examiner.

